Method of recording and reproducing phonofilms



March 14, 1933. A, KAROLUS 1,901,033

METHOD oF RECORDING AND REPRODUCING PHoNoFILMs Filed April 24, 1929 Izq, i

INVENTOR AUGUST KAROLUS BY Wm AT Y Patented q Mar. 174, 1933 UNITED lSTATES PATET Erice AUGUST KARoLUs, or LEIPZIG, GERMANY, AssIcfNoR To RAnIo coREoRATroN or AMERICA, A CORPORATION or DELAWARE METHOD 0F RECORDING AND RERRonUciNG PHoNoEILMs Application filed April 24, 1929, Serial No. 357,859, and in Germany May 19, 1928. l

In the recording and reproduction of sound upon and from moving films in accordance with the prior art, a single slit has been usually employed. This slit hady to be made very narrow in the direction of the movement of the film in order that the photographic impression and photoelectric reproduction of the high frequencies required would be clear and the quality of the voice or music would be good while keeping the speed of film travel inside of moderate limits. The result of this is that the lower frequencies fail to receive proper treatment.

It is an obj ect of this invention to overcome this difiiculty.

Itis another object of this invention to produce a method of and means for recording and reproducing of phono-films in which the reproduction will be more faithful.

Another object Vof my invention is to record and reproduce sound upon and from moving films in such a manner that in reproduction the energy derived from low frequency sounds will be in proper proportion to that derived from high frequency sounds, as will be more clearly set forth hereinafter.

The present invention comprises the separation of the vocal and instrumental frequencies in two frequency bands. Such separaytion is accomplished, for instance, by electrical means by the use of two band passfilters. The low frequencies are brought to act upon a light valve with a comparatively wide slit or gap, and this results ina corresponding acoustic record upon the film. Another light relay is similarly controlled by the high vfrequencies and provided with a narrow slit producing an adjacent acoustic record upon the same film. Thus the former band will contain the lower frequencies with greater volume, and the second band will contain the higher frequencies.

For the reproduction with photoelectric cells, it is only necessary to throw-the light through the film upon a single cell, though with the use of two convenient slits, one

thereof being of greater width for the lower ranges of frequencies, and the other of less width for the high frequencies. The light passed through both photoelectric bands on the film becomes superimposed in the cell and regulate the low and high frequencies under amplitude relations which will be equally favorable to both frequency ranges.

Having thus briefly described my invention, attention is now called to the drawing in whichz' Y Fig. 1 is a diagram showing the method of recording in accordance with my. invention;

And FiO. 2 is a schematic View and `dia#- gram show the method of* reproducing in accordance with my invention.

Referring now more particularly to Fig.,1, fdenotes the microphone and 2 an amplifier for the microphone currents. Filters 3 and f1 serve for the separation of the high and low frequency band.' Amplifiers 5y and 6 amplify the currents passing through the filters 3 andn respectively, and supply currents to the light control arrangements in this instance represented as Kerr cells 7 and 8,. The former is arranged with a narrow' slit and the latterk with a wide slit. The resulting bands upon the film are indicated by thek bands 9 and 10 upon the photographick film 11.

Referring now more particularly to Fig.

2, 12 and 13 are the two slits corresponding 14 is amplified by the amplifier 15 and re.- i

produced in theloud speaker 16.

I will now briefly describe theoperation of my invention. rfhe microphonic currents are divided by the filters 3 and 4 into high and low frequency bands and after ampli1ication serve to control the amount of light reaching the moving film 11. The light con;

trolled by the low frequency band passes vto the film through a wide slot, whereas the light controlled by the high frequency band reaches the film through a narrow slot. In' reproduction this process is reversed except that the energy generated by light falling throughl both bands is combined yby perinitting this light to fall upon the same photoelectric cell, the resistance of which is thus varied in accordance With the tota-l light.

Having thus described my invention, it is to be understood that I do not desire to be [limited by the specific embodiment shown sity of the light beams on amoving film record, restricting the light pern itted to fall upon the moving film record from the light beam controlled by the high frequency to a small area With respect to the line of motion of said film, restricting the liht permitted to fall upon the moving lm record from the light beam controlled by the low frequency to a relatively large area with respect to the line v of motion of said film, thus producing tWo records upon said film, passinghght through the two records, restricting the light passing through each record in the same manner as in the recording, and photoelectrically `controlling a single electric current in accordance with the total amount ofV light passing through the film record, and reproducing the originally recorded sound-thereby.

2. The method of photographic recording and reproduction of sound which comprises separating the high and low frequency components of the electric impulses representing said sound, controlling, the intensity of a light beam in accordance With each of said frequency components, independently recording the intensity of the said light beams upon a moving film record, restricting the light permitted to fall upon the moving record from the light beams controlled by the high and lou/frequencies to a small and relatively v large area, respectively, with respect to the line of motion of said film, thus producing two records upon said film, passing light through the tivo records restricting the light passing through each record in the same manner as in the recording, and photoelectrically ing means fory restricting the light used to record the 'high and loW vfrequency components falling upon the film to relatively narrow and Wide slots With respect to the direction of travel of the film and reproducing apparatus including means for similarly restricting the light passing through the tvvo records, a common photoelectric element adapted to be actuated by the amount of lighty passing through the film, andrepro, ducing apparatus controlled by said photoelectric cell. v

4. A photographic sound reproducing method including producing relatively large and relatively small light beams, modulating said relatively large light beam in accordance with the lowv frequency component of the sound to be reproduced, modulating said relatively small `light beam in accordance With the high frequency component of said, sound, and utilizing the total illumination of said-modulated beams to produce an electric current dependent on said components.

AUGUST nanoLUs.

controlling an electric current in accordance with the total amount of light passing through the two records.

pendently recording the high and low frequency components photoelectrically, includ- 

